Enabling intensification of multiphase chemical processes with additive manufacturing.

Fixed bed supports of various materials (metal, ceramic, polymer) and geometries are used to enhance the performance of many unit operations in chemical processes. Consider first metal and ceramic monolith support structures, which are typically extruded. Extruded monoliths contain regular, parallel channels enabling high throughput because of the low pressure drop accompanying high flow rate. However, extruded channels have a low surface-area-to-volume ratio resulting in low contact between the fluid phase and the support. Additive manufacturing, also referred to as three dimensional printing (3DP), can be used to overcome these disadvantages by offering precise control over key design parameters of the fixed bed including material-of-construction and total bed surface area, as well as accommodating system integration features compatible with continuous flow chemistry. These design parameters together with optimized extrinsic process conditions can be tuned to prepare customizable separation and reaction systems based on objectives for chemical process and/or the desired product. We discuss key elements of leveraging the flexibility of additive manufacturing to intensification with a focus on applications in continuous flow processes and disperse, multiphase systems enabling a range of scalable chemistry spanning discovery to manufacturing operations.

An ab Initio Exploration of the Bergman Cyclization.

The Bergman cyclization is an important reaction in which an enediyne cyclizes to produce a highly reactive diradical species, p-benzyne. Enediyne motifs are found in natural antitumor antibiotic compounds, such as calicheammicin and dynemicin. Understanding the energetics of cyclization is required to better control the initiation of the cyclization, which induces cell death. We computed the singlet and triplet potential energy surfaces for the Bergman cyclization of (Z)-hex-3-ene-1,5-diyne using the CCSD and EOM-SF-CCSD methods. The triplet enediyne and transition state were found to have C2 symmetry, which contrasts with the singlet reactant and transition state that possess C2v symmetry. We analyzed the frontier orbitals of both cyclization pathways to explain the large energetic barrier of the triplet cyclization. Reaction energies were calculated using CCSD(T)/cc-pVTZ single-point calculations on structures optimized with CCSD/cc-pVDZ. The singlet reaction was found to be slightly endothermic (ΔHrxn = 13.76 kcal/mol) and the triplet reaction was found to be highly exothermic (ΔHrxn = -33.29 kcal/mol). The adiabatic singlet-triplet gap of p-benzyne, computed with EOM-SF-CCSD/cc-pVTZ, was found to be 3.56 kcal/mol, indicating a singlet ground state.